Many folders used in web printing presses use driven belts or tapes to transport signatures from the cut cylinder to the next operation, such as signature deceleration or folding. These tapes contact the web or ribbons before the signature is created and have a velocity higher than that of the ribbon. The velocity difference causes relative motion (scrubbing) between the ribbons and tapes.
After a signature is created by the cut cylinder, the signature is accelerated by the tapes from ribbon or web speed, which generally matches the surface speed of the cut cylinder as well, to tape speed. The rate of signature acceleration depends on the mass of the signatures and on the normal force and coefficient of friction between the tapes and signatures. Variations in these factors cause position variations in the signatures when they reach the next device, such as a fan or jaw cylinder. Position variations include: signature-to-signature variation at a given press speed, variations due to press speed changes, and variations over time due to, for example, tape wear. Position variations cause the following problems: reduced maximum allowable press speed, increased need for manual phase adjustments, machine damage, and press downtime due to jammed signatures. Such problems are worse in variable cutoff applications and become worse as press speeds increase.
U.S. Pat. No. 4,919,027 shows a sheet diverting system and U.S. Pat. No. 6,612,213 shows a belt diverter. Both are hereby incorporated by reference herein.